Saturn’s moon Titan, shrouded in a crust of ice that could harbour a liquid ocean, just became a little more mysterious.
Measurements have revealed that the moon is moving away from Saturn 100 times faster than scientists had believed.
The finding could throw light on one of the mysteries of the solar system: how Saturn and its famous rings (and 80 moons) formed.
Our own moon drifts 1.5 inches from Earth each year – but Titan is drifting at four inches per year, hinting that it was born much closer to Saturn.
Titan slowly migrated out to 746,000 miles away from Saturn over 4.5 billion years, according to two separate sets of measurements.
Dr Jim Fuller, of Caltech, said: “This implies that the Saturnian moon system, and potentially its rings, have formed and evolved more dynamically than previously believed.”
While scientists know that Saturn formed 4.6 billion years ago in the early days of the solar system, there's more uncertainty about when the planet's rings and its system of more than 80 moons formed.
The revised rate of its drift suggests that the moon started out much closer to Saturn, which would mean the whole system expanded more quickly than previously believed.
“This result brings an important new piece of the puzzle for the highly debated question of the age of the Saturn system and how its moons formed,” said Valery Lainey, lead author of the work published in Nature Astronomy.
Two teams of researchers each used a different technique to measure Titan’s orbit over a period of 10 years.
One technique, called astrometry, produced precise measurements of Titan’s position relative to background stars in images taken by the Cassini spacecraft.
The other technique, radiometry, measured Cassini’s velocity as it was affected by the gravitational influence of Titan.
Valéry Lainey, of Nasa’s Jet Propulsion Laboratory (JPL), said: “By using two completely independent data sets – astrometric and radiometric – and two different methods of analysis, we obtained results that are in full agreement.”